The study is concerned with qualitative and quantitative cytologic evaluation of cells exfoliated from transitional cell carcinomas as well as with cytochemical studies on the same material. Nucleopore filter preparations are being made from all urine specimens in the study and the ratio of normal cells to atypical cells to clearly neoplastic cells are determined. The total number of neoplastic cells, cell-to-cell relationships and various cellular and nuclear features are also being studied. In addition, 100 characteristic cells and nuclei per case are measured planimetrically, in an attempt to more clearly determine the relative nuclear sizes of well differentiated carcinomas as compared to normal bladder mucosa or poorly differentiated carcinomas. The cytochemical studies are principally concerned with the changes that may occur at the surfaces of neoplastic cells. On 30 biopsies, the staining of cell surfaces by phosphotungstic acid (PTA) at low pH or colloidal iron hydroxide (CIH) were investigated. These 30 biopsies include a wide range of pathologic states including normal epithelium, non-invasive grade I papillomas and higher grades of invasive bladder cancers. The preliminary results indicate that in each biopsy, the staining of cell surfaces by PTA and CIH is similar. Thus PTA as well as CIH appears to be reacting with sialic acid residues at cell surfaces. The distribution of stain is similar for papillomas and normal epithelium while the epithelium of less well differentiated tumors generally exhibits a decreased amount of PTA or CIH surface material. Thus surfaces of invasive bladder carcinoma cells appear to be deficient in sailic acid. Additional data on cell surface staining will be obtained. Autoradiographic experiments, designed to study the incorporation of radioactive sugars into surface coat material of normal and neoplastic bladder epithelium, will also be carried out.